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Commit cb96143d authored by Michael Ellerman's avatar Michael Ellerman Committed by Benjamin Herrenschmidt
Browse files

selftests: Add test of PMU instruction counting on powerpc 



This commit adds a test of instruction counting using the PMU on powerpc.

Although the bulk of the code is architecture agnostic, the code needs to
run a precisely sized loop which is implemented in assembler.

Signed-off-by: default avatarMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 2fae0d7c

tools/testing/selftests/powerpc/Makefile

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@@ -13,7 +13,7 @@ CFLAGS := -Wall -O2 -flto -Wall -Werror -DGIT_VERSION='"$(GIT_VERSION)"' -I$(CUR 


export CC CFLAGS



TARGETS =

TARGETS = pmu



endif

tools/testing/selftests/powerpc/pmu/Makefile

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noarg:

	$(MAKE) -C ../



PROGS := count_instructions

EXTRA_SOURCES := ../harness.c event.c



all: $(PROGS)



$(PROGS): $(EXTRA_SOURCES)



# loop.S can only be built 64-bit

count_instructions: loop.S count_instructions.c $(EXTRA_SOURCES)

	$(CC) $(CFLAGS) -m64 -o $@ $^



run_tests: all

	@-for PROG in $(PROGS); do \

		./$$PROG; \

	done;



clean:

	rm -f $(PROGS) loop.o



.PHONY: all run_tests clean

tools/testing/selftests/powerpc/pmu/count_instructions.c

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Original line number Diff line number Diff line 
/*

 * Copyright 2013, Michael Ellerman, IBM Corp.

 * Licensed under GPLv2.

 */



#define _GNU_SOURCE



#include <stdio.h>

#include <stdbool.h>

#include <string.h>

#include <sys/prctl.h>



#include "event.h"

#include "utils.h"



extern void thirty_two_instruction_loop(u64 loops);



static void setup_event(struct event *e, u64 config, char *name)

{

	event_init_opts(e, config, PERF_TYPE_HARDWARE, name);



	e->attr.disabled = 1;

	e->attr.exclude_kernel = 1;

	e->attr.exclude_hv = 1;

	e->attr.exclude_idle = 1;

}



static int do_count_loop(struct event *events, u64 instructions,

			 u64 overhead, bool report)

{

	s64 difference, expected;

	double percentage;



	prctl(PR_TASK_PERF_EVENTS_ENABLE);



	/* Run for 1M instructions */

	thirty_two_instruction_loop(instructions >> 5);



	prctl(PR_TASK_PERF_EVENTS_DISABLE);



	event_read(&events[0]);

	event_read(&events[1]);



	expected = instructions + overhead;

	difference = events[0].result.value - expected;

	percentage = (double)difference / events[0].result.value * 100;



	if (report) {

		event_report(&events[0]);

		event_report(&events[1]);



		printf("Looped for %llu instructions, overhead %llu\n", instructions, overhead);

		printf("Expected %llu\n", expected);

		printf("Actual   %llu\n", events[0].result.value);

		printf("Delta    %lld, %f%%\n", difference, percentage);

	}



	event_reset(&events[0]);

	event_reset(&events[1]);



	if (difference < 0)

		difference = -difference;



	/* Tolerate a difference below 0.0001 % */

	difference *= 10000 * 100;

	if (difference / events[0].result.value)

		return -1;



	return 0;

}



/* Count how many instructions it takes to do a null loop */

static u64 determine_overhead(struct event *events)

{

	u64 current, overhead;

	int i;



	do_count_loop(events, 0, 0, false);

	overhead = events[0].result.value;



	for (i = 0; i < 100; i++) {

		do_count_loop(events, 0, 0, false);

		current = events[0].result.value;

		if (current < overhead) {

			printf("Replacing overhead %llu with %llu\n", overhead, current);

			overhead = current;

		}

	}



	return overhead;

}



static int count_instructions(void)

{

	struct event events[2];

	u64 overhead;



	setup_event(&events[0], PERF_COUNT_HW_INSTRUCTIONS, "instructions");

	setup_event(&events[1], PERF_COUNT_HW_CPU_CYCLES, "cycles");



	if (event_open(&events[0])) {

		perror("perf_event_open");

		return -1;

	}



	if (event_open_with_group(&events[1], events[0].fd)) {

		perror("perf_event_open");

		return -1;

	}



	overhead = determine_overhead(events);

	printf("Overhead of null loop: %llu instructions\n", overhead);



	/* Run for 1M instructions */

	FAIL_IF(do_count_loop(events, 0x100000, overhead, true));



	/* Run for 10M instructions */

	FAIL_IF(do_count_loop(events, 0xa00000, overhead, true));



	/* Run for 100M instructions */

	FAIL_IF(do_count_loop(events, 0x6400000, overhead, true));



	/* Run for 1G instructions */

	FAIL_IF(do_count_loop(events, 0x40000000, overhead, true));



	event_close(&events[0]);

	event_close(&events[1]);



	return 0;

}



int main(void)

{

	return test_harness(count_instructions, "count_instructions");

}

tools/testing/selftests/powerpc/pmu/event.c

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/*

 * Copyright 2013, Michael Ellerman, IBM Corp.

 * Licensed under GPLv2.

 */



#define _GNU_SOURCE

#include <unistd.h>

#include <sys/syscall.h>

#include <string.h>

#include <stdio.h>

#include <sys/ioctl.h>



#include "event.h"





int perf_event_open(struct perf_event_attr *attr, pid_t pid, int cpu,

		int group_fd, unsigned long flags)

{

	return syscall(__NR_perf_event_open, attr, pid, cpu,

			   group_fd, flags);

}



void event_init_opts(struct event *e, u64 config, int type, char *name)

{

	memset(e, 0, sizeof(*e));



	e->name = name;



	e->attr.type = type;

	e->attr.config = config;

	e->attr.size = sizeof(e->attr);

	/* This has to match the structure layout in the header */

	e->attr.read_format = PERF_FORMAT_TOTAL_TIME_ENABLED | \

				  PERF_FORMAT_TOTAL_TIME_RUNNING;

}



void event_init_named(struct event *e, u64 config, char *name)

{

	event_init_opts(e, config, PERF_TYPE_RAW, name);

}



#define PERF_CURRENT_PID	0

#define PERF_NO_CPU		-1

#define PERF_NO_GROUP		-1



int event_open_with_options(struct event *e, pid_t pid, int cpu, int group_fd)

{

	e->fd = perf_event_open(&e->attr, pid, cpu, group_fd, 0);

	if (e->fd == -1) {

		perror("perf_event_open");

		return -1;

	}



	return 0;

}



int event_open_with_group(struct event *e, int group_fd)

{

	return event_open_with_options(e, PERF_CURRENT_PID, PERF_NO_CPU, group_fd);

}



int event_open(struct event *e)

{

	return event_open_with_options(e, PERF_CURRENT_PID, PERF_NO_CPU, PERF_NO_GROUP);

}



void event_close(struct event *e)

{

	close(e->fd);

}



int event_reset(struct event *e)

{

	return ioctl(e->fd, PERF_EVENT_IOC_RESET);

}



int event_read(struct event *e)

{

	int rc;



	rc = read(e->fd, &e->result, sizeof(e->result));

	if (rc != sizeof(e->result)) {

		fprintf(stderr, "read error on event %p!\n", e);

		return -1;

	}



	return 0;

}



void event_report_justified(struct event *e, int name_width, int result_width)

{

	printf("%*s: result %*llu ", name_width, e->name, result_width,

	       e->result.value);



	if (e->result.running == e->result.enabled)

		printf("running/enabled %llu\n", e->result.running);

	else

		printf("running %llu enabled %llu\n", e->result.running,

			e->result.enabled);

}



void event_report(struct event *e)

{

	event_report_justified(e, 0, 0);

}

tools/testing/selftests/powerpc/pmu/event.h

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/*

 * Copyright 2013, Michael Ellerman, IBM Corp.

 * Licensed under GPLv2.

 */



#ifndef _SELFTESTS_POWERPC_PMU_EVENT_H

#define _SELFTESTS_POWERPC_PMU_EVENT_H



#include <unistd.h>

#include <linux/perf_event.h>



#include "utils.h"





struct event {

	struct perf_event_attr attr;

	char *name;

	int fd;

	/* This must match the read_format we use */

	struct {

		u64 value;

		u64 running;

		u64 enabled;

	} result;

};



void event_init(struct event *e, u64 config);

void event_init_named(struct event *e, u64 config, char *name);

void event_init_opts(struct event *e, u64 config, int type, char *name);

int event_open_with_options(struct event *e, pid_t pid, int cpu, int group_fd);

int event_open_with_group(struct event *e, int group_fd);

int event_open(struct event *e);

void event_close(struct event *e);

int event_reset(struct event *e);

int event_read(struct event *e);

void event_report_justified(struct event *e, int name_width, int result_width);

void event_report(struct event *e);



#endif /* _SELFTESTS_POWERPC_PMU_EVENT_H */